The present invention relates to disc brakes of the type in which the brakes are actuated by spring pressure, and are released by application of fluid pressure to one side of an actuating piston. Brakes of this type are widely used on heavy machinery, such as cranes, rolling mill equipment, bridge machinery, elevators, belt conveyors, trams, and the like.
More specifically, the invention pertains to a clearance-takeup device whereby all excessive clearances in the system are automatically and continuously taken up, so that the springs actuating the brake require only a minimum extension before the friction pads are solidly engaged against their respective frictional surfaces on the brake disc. The springs are thus enabled to exert the maximum pressure against the friction pads, regardless of wear on the friction pads, or other conditions that might tend to increase the clearances. With spring-actuated brakes, it is essential that the springs exert a constant spring force against the friction pads at all times, and this requires that the springs act through constant distance of extension between the fully-released and fully-applied conditions.
Spring-actuated disc brakes are known in the art, and various attempts have been made to provide automatic clearance-takeup devices for the same, so as to maintain a more-or-less constant air gap between the friction pads and the disc surfaces. However, none of these clearance-takeup devices has been entirely satisfactory for various reasons. In some cases, the devices have been complicated and expensive to manufacture and service. In other cases, they have been lacking in sensitivity and reliability. Another objectionable characterisitc of some prior devices has been a tendency of the clearance-takeup mechanism to overadjust, with the result that the brake cannot be fully released. As a consequence, the brake drags and wears excessively, and power is wasted driving the machinery against the frictional drag of the brake.